We shall attempt to obtain additional evidence for the proposed role of glutamine synthetase as repressor and activator of its synthesis. This will be accomplished by a study of the kinetics of derepression of GS in wild type and mutant strains, by fusing the glnA gene to lac in order to study activation or repression in merodiploids, and by the isolation of new types of mutants that suppress the phenotype produced by mutations in nut and in glnF. We hope to prepare in this manner the ground for the identification of the products of these genes and of their function.